Okay, this post is centered more around the anime than the novels or manga, but it's all related, of course. There is even mention of the spin off series!
“Shield Hero's popularity has lead to the inevitable: a spin-off! A light novel known as The Reprise of the Spear Hero, the story follows Motoyasu after he dies and returns to life, learning his spear has the ability Time Reversal. Armed with his knowledge of the past, Motoyasu aims to help Naofumi in any way he can. Unfortunately, Motoyasu's kind of a screw-up so he winds up going through several time-reversed loops as other Heroes die around him, causing him to have to do everything over again.”
Original article here: